Typically, large client-server computer network systems exhibit topology having a single file server that acts as the center of the system's operations. The file-server is usually based on a microprocessor, and is dedicated to handling large data manipulation and flow as requested by a number of clients. Clients, or client nodes, may be a number of different electronic devices including but not limited to: desktop workstations, personal computers, mainframe or minicomputers, telecommunication equipment and dumb terminals. System resources are typically provided by large electronic storage devices associated with the file server. These resources include data, application programs for clients, and the network operating system. The file server, operating according to the network operating system, performs traffic management functions and provides security for the data. The file server also performs information retrieval and may do computations or specific record searches within a database.
Client nodes and file servers in computerized networks such as Ethernet, ARCnet and AppleTalk must be connected via a transmission medium, commonly some form of cabling. The physical layout (topology) of a large client-server network routes all client requests to the file server. Conventional bus systems limit the number of direct connections. To maintain an acceptable degree of connectivity such networks typically employ a hub or concentrator connection as a subsystem. The hub serves as a junction box for connected nodes and passes the data between client and file server by a separate dedicated network trunk. Large network systems may have layered hubs to provide connectivity to more nodes while still using a single file server.
The file server is limited by the bus connection to a conventional network during periods of heavy client use. As demand increases, data throughput to and from clients saturates, and system performance is limited. To maintain acceptable performance, conventional networks have incorporated second level servers that perform limited functions of the primary server and eliminate waiting by clients in some cases. Typically, data is stored separate from the primary server and later, at a convenient time, such as once a day or perhaps as often as once an hour, the secondary server downloads to the primary file server. In these systems, real time operation is not possible. Also, at higher demand the bus systems for both the second-level servers as well as the primary server saturate, and system-wide performance is again limited.
What is needed is a computer network architecture that maintains substantially real time performance for large numbers of clients and resources.